Two-stage process for producing oil from microalgae

Abstract

A process for production of biofuels from algae can include cultivating an oil-producing algae by promoting sequential photoautotrophic and heterotrophic growth. The method can further include producing oil by heterotrophic growth of algae wherein the heterotrophic algae growth is achieved by introducing a sugar feed to the oil-producing algae. An algal oil can be extracted from the oil-producing algae, and can be converted to form biodiesel.

What is claimed is: 
     
       1. A process for production of biofuels from algae, comprising:
 a) inducing algae cell body production of an oil-producing algae by photoautotrophic growth; 
 b) initiating heterotrophic growth of the oil-producing algae using a stress induction mechanism; 
 c) inducing algal oil production by heterotrophic growth of the oil-producing algae, wherein the heterotrophic growth includes introducing a sugar feed to the oil-producing algae; and 
 d) extracting an algal oil from the oil-producing algae, wherein the algal oil is extracted by either mechanically rupturing or biologically rupturing an algae cell wall, an oil vesicle wall, or a combination thereof. 
 
     
     
       2. The method of  claim 1 , further comprising converting the oil to biodiesel. 
     
     
       3. The process of  claim 1 , wherein the oil-producing algae includes a member selected from the group consisting of diatoms (bacillariophytes), green algae (chlorophytes), blue-green algae (cyanophytes), golden-brown algae (chrysophytes), haptophytes, and combinations thereof. 
     
     
       4. The process of  claim 3 , wherein the oil-producing algae includes  Amphipleura, Amphora, Chaetoceros, Cyclotella, Cymbella, Fragilaria, Hantzschia, Navicula, Nitzschia, Phaeodactylum, Thalassiosira, Ankistrodesmus, Botryococcus, Chlorella, Chlorococcum, Dunaliella, Monoraphidium, Oocystis, Scenedesmus, Tetraselmis, Oscillatoria, Synechococcus, Boekelovia , or combinations thereof. 
     
     
       5. The process of  claim 4 , wherein the oil-producing algae includes  Chlorella, Dunaliella , or combinations thereof. 
     
     
       6. The process of  claim 1 , further comprising introducing a nitrogen-fixing algae to the oil-producing algae to provide nitrogen as a nutrient. 
     
     
       7. The process of  claim 1 , wherein the oil-producing algae includes a nitrogen-fixing algae. 
     
     
       8. The process of  claim 7 , wherein the nitrogen-fixing algae includes cyanobacteria. 
     
     
       9. The process of  claim 1 , wherein the sugar feed is the primary source of both carbon and energy in the heterotrophic growth stage. 
     
     
       10. The process of  claim 1 , wherein introducing the sugar feed further includes cultivating algae and extracting the sugar feed therefrom. 
     
     
       11. The process of  claim 1 , wherein the stress induction mechanism includes at least one of light deprivation, nutrient deprivation, injection of a reactive oxygen source, a lipid trigger, and chemical additives. 
     
     
       12. The process of  claim 1 , wherein the photoautotrophic growth stage and the heterotrophic growth stage overlap in time. 
     
     
       13. The process of  claim 1 , wherein the photoautotrophic growth stage and the heterotrophic growth stage are performed substantially simultaneously. 
     
     
       14. The process of  claim 13 , wherein the nitrogen-fixing algae includes cyanobacteria. 
     
     
       15. The process of  claim 1 , wherein the algal oil is extracted by mechanically rupturing an algae cell wall, an oil vesicle wall, or a combination thereof. 
     
     
       16. The process of  claim 1 , wherein the algal oil is extracted by biologically rupturing an algae cell wall, and oil vesicle wall, or a combination thereof. 
     
     
       17. The process of  claim 16 , wherein the biologically rupturing comprises applying a biological agent to the algal cell wall, oil vesicle wall, or combination thereof. 
     
     
       18. The process of  claim 17 , wherein the biological agent is a virus. 
     
     
       19. The process of  claim 1 , wherein extracting further comprises forming a slurry of algae debris material and separating the algal oil from a cellular residue. 
     
     
       20. The process of  claim 19 , wherein separating the algal oil from a cellular residue comprising centrifuging the slurry of algal debris material.